1. Technical Field
The invention relates to a measuring system for determining a distance between a sensor device and a measured object, wherein the sensor device comprises a light source for generating an illumination light beam and a detector for detecting a portion of the illumination light beam reflected on the surface of the measured object and wherein the measured object is designed so it is transparent at least for a wavelength range of the visible light.
The invention also relates to a measuring system for determining a distance between a sensor device and a measured object, wherein the sensor device comprises a light source for generating an illumination light beam and a detector for detecting a portion of the illumination light beam reflected on the surface of the measured object and wherein the measured object is designed in such a way that visible light is reflected directly.
2. Description of Related Art
Optical measuring systems have wide-ranging applications in practice. The contactless measurement that is precise and still fast opens up a number of application areas in which the distance between a measured object and a sensor device will be measured contactlessly or measure a measured object without wear. One important application area is quality assurance, in which the quality of a workpiece is tested.
In optical measuring systems, a measured object is illuminated with an illumination light beam—very frequently a red or infrared laser beam—and the portion of the illumination light beam reflected on the measured object is detected with a detector. Various methods are known from experience, according to which the distance of the measured object from the sensor device can be determined with such a sensor device. Reference is made to a triangulation measurement as an example.
The known measuring systems from the state of the art are always problematic if measurements are done on transparent or partially transparent measured objects. In this context, transparent means that broad spectral portions of the visible light (wavelength range between 400 nm and 800 nm) can pass through the measured object. During the passage, the spectral portions are only attenuated to a slight extent. Partially transparent means that at least one spectral portion of the visible light can pass through the measured object while another spectral portion of the visible light is absorbed or reflected completely or to an extent that is not inconsiderable.
If an illumination light beam falls on measured objects of this type, it is reflected directly, i.e. the angle of incidence of the illumination light beam on the surface of the measured object is equal to the angle of reflection of the reflected illumination light beam. Scatter in other spatial directions practically does not exist. Because of this, sensor device and measured object must be aligned to each other optimally so that a measurement leads to results that are usable. If the surface of the measured object is tipped out of the optimal position only slightly, the illumination light beam is not reflected to the detector. The measuring process fails and is considerably unstable. An optimal alignment of the sensor device and of the measured object with respect to each other is practically impossible to ensure, especially in quality assurance in manufacturing environments. This alignment is practically impossible with curved or rounded measured objects. Similar problems occur with optical measurement on non-transparent measured objects that do not reflect light directly because of their surface finish. The problems are comparable here. As an example, reference is made to mirroring surfaces.